| 9 | ÷ | ( | 9 | + | a | ) | + | 4 | ÷ | ( | 4 | + | a | ) | = | 1 |
| Multiply both sides of the equation by: | ( | 9 | + | a | ) |
| 9 | + | 4 | ÷ | ( | 4 | + | a | ) | × | ( | 9 | + | a | ) | = | 1 | ( | 9 | + | a | ) |
| 9 | + | 4 | ÷ | ( | 4 | + | a | ) | × | 9 | + | 4 | ÷ | ( | 4 | + | a | ) | × | a | = | 1 | ( | 9 | + | a | ) |
| 9 | + | 4 | ÷ | ( | 4 | + | a | ) | × | 9 | + | 4 | ÷ | ( | 4 | + | a | ) | × | a | = | 1 | × | 9 | + | 1 | a |
| 9 | + | 36 | ÷ | ( | 4 | + | a | ) | + | 4 | ÷ | ( | 4 | + | a | ) | × | a | = | 9 | + | 1 | a |
| Multiply both sides of the equation by: | ( | 4 | + | a | ) |
| 9 | ( | 4 | + | a | ) | + | 36 | + | 4 | a | = | 9 | ( | 4 | + | a | ) | + | 1 | a | ( | 4 | + | a | ) |
| 9 | × | 4 | + | 9 | a | + | 36 | + | 4 | a | = | 9 | ( | 4 | + | a | ) | + | 1 | a | ( | 4 | + | a | ) |
| 9 | × | 4 | + | 9 | a | + | 36 | + | 4 | a | = | 9 | × | 4 | + | 9 | a | + | 1 | a | ( | 4 | + | a | ) |
| 36 | + | 9 | a | + | 36 | + | 4 | a | = | 36 | + | 9 | a | + | 1 | a | ( | 4 | + | a | ) |
| 72 | + | 13 | a | = | 36 | + | 9 | a | + | 1 | a | ( | 4 | + | a | ) |
| 72 | + | 13 | a | = | 36 | + | 9 | a | + | 1 | a | × | 4 | + | 1 | a | a |
| 72 | + | 13 | a | = | 36 | + | 9 | a | + | 4 | a | + | 1 | a | a |
| 72 | + | 13 | a | = | 36 | + | 13 | a | + | 1 | a | a |